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Find the coefficient of the 
x^(2) term in the binomial expansion of 
(4x+2)^(4).

Find the coefficient of the x2 x^{2} term in the binomial expansion of (4x+2)4 (4 x+2)^{4} .

Full solution

Q. Find the coefficient of the x2 x^{2} term in the binomial expansion of (4x+2)4 (4 x+2)^{4} .
  1. Use Binomial Theorem: To find the coefficient of the x2x^2 term in the binomial expansion of (4x+2)4(4x+2)^4, we will use the Binomial Theorem, which states that (a+b)n(a+b)^n expands to a sum of terms in the form of C(n,k)a(nk)bkC(n, k) \cdot a^{(n-k)} \cdot b^k, where C(n,k)C(n, k) is the binomial coefficient "nn choose kk". We are looking for the term where the power of xx is 22, which means we need the term where k=2k = 2.
  2. Calculate Binomial Coefficient: The binomial coefficient C(n,k)C(n, k) for the term where k=2k = 2 is C(4,2)C(4, 2). This can be calculated as 4!2!(42)!=(4×3×2×1)(2×1×2×1)=6\frac{4!}{2!(4-2)!} = \frac{(4 \times 3 \times 2 \times 1)}{(2 \times 1 \times 2 \times 1)} = 6.
  3. Find the Term: Now we need to find the actual term. The term with x2x^2 will have a power of 22 for xx and a power of 22 for the constant term. Therefore, the term is C(4,2)×(4x)2×22C(4, 2) \times (4x)^2 \times 2^2.
  4. Calculate the Term: Calculating the term: 6×(4x)2×22=6×16x2×4=6×64x2=384x26 \times (4x)^2 \times 2^2 = 6 \times 16x^2 \times 4 = 6 \times 64x^2 = 384x^2.
  5. Determine Coefficient: The coefficient of the x2x^2 term is therefore 384384.

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